File tailer webhook is based on a Mutating Admission Webhook which gets called every time when a pod starts, and will be triggered when a pod specification contains an annotation with the sidecar.logging-extensions.banzaicloud.io/tail key. For example:
apiVersion: v1
kind: Pod
metadata:
name: test-pod
annotations: {"sidecar.logging-extensions.banzaicloud.io/tail": "/var/log/date"}
spec:
containers:
- image: debian
name: sample-container
command: ["/bin/sh", "-c"]
args:
- while true; do
date >> /var/log/date;
sleep 1;
done
- image: debian
name: sample-container2
...
Note: if the pod contains multiple containers, see Multi-container pods.
About the File Tailer Webhook annotation 🔗︎
The basic format of a file tailer webhook annotation is the following:
| Key | sidecar.logging-extensions.banzaicloud.io/tail |
| Value | Files to be tailed separated by commas |
For example:
...
metadata:
name: test-pod
annotations: {"sidecar.logging-extensions.banzaicloud.io/tail": "/var/log/date,/var/log/mycustomfile"}
spec:
...
Multi-container pods 🔗︎
In some cases you have multiple containers in your pod and you want to distinguish which file annotation belongs to which container. You can order every file annotations to particular container by prefixing the annotation with a ${ContainerName}: container key. For example:
...
metadata:
name: test-pod
annotations: {"sidecar.logging-extensions.banzaicloud.io/tail": "sample-container:/var/log/date,sample-container2:/var/log/anotherfile,/var/log/mycustomfile,foobarbaz:/foo/bar/baz"}
spec:
...
CAUTION:
- Annotations without containername prefix: the file gets tailed on the default container (container 0)
- Annotations with invalid containername: file tailer annotation gets discarded
| Annotation | Explanation |
|---|---|
| sample-container:/var/log/date | tails file /var/log/date in sample-container |
| sample-container2:/var/log/anotherfile | tails file /var/log/anotherfile in sample-container2 |
| /var/log/mycustomfile | tails file /var/log/mycustomfile in default container (sample-container) |
| foobarbaz:/foo/bar/baz | will be discarded due to non-existing container name |
